Shiki Saber is an AOE Arts NP spam Saber with a few additional tools in her kit. Possessing the only invulnerability pierce NP of any Saber currently implemented in the game, her damage output is still strikingly consistent regardless of buffs thrown in its path thanks to the combo of invulnerability and defense pierce. With a steady star supply she can recharge her NP gauge with relative ease, and expend it if necessary using her powerful self heal.

She may struggle to compete with vanilla Nero after the Roman’s NP interlude, but her high debuff resistance, low cooldown, heal, and ever-consistent NP always give her a niche.

Strengths

A strong Arts boost from her Mystic Eyes of Death Perception skill and her passive Arts card boost on an Arts AoE NP, Saber Shiki has very strong NP gain, furthered by her above-average Quick card and Extra card NP gain.

Arguably the most consistent instant death AoE NP in the game, Saber Shiki can eviscerate entire waves of foes so long as they’re bronze and not Servants.

In spite of her double damage buffs, Saber Shiki’s damage output pales in comparison to her SSR and SR competitors. In a vacuum there’s little reason to deploy her over existing competitors if seeking sheer damage.

Saber Shiki’s heal can be difficult to find use for, especially if not NP2 or higher, since using the skill essentially denies her own NP on the same turn.

She lacks any form of defensive buff or hard defensive skill like a dodge to avoid NP damage, making her dependant on her allies for that form of defence.

Formalcraft / Projection: While Saber Shiki has plenty of Arts boosters already, more doesn’t hurt. Her good NP gain means it isn’t too much of a sacrifice to miss out on starting NP gauge, and it aids in her ability to perform back-to-back NPs in a NPAA or NPQA chain.

Halloween Princess: Getting a solid NP damage buff will increase Saber Shiki’s NP damage output, while the starting NP gauge lets her pop off her first NP much sooner.

Little Halloween Devil / Divine Banquet: Multiplying together with Saber Shiki’s Arts boosters for immense NP gain, these CE’s can really let Saber Shiki’s NP spam power come into its own, at the cost of the damage benefits she may gain otherwise.

Black Grail: Only really recommended as her 5k hp per 4 turns heal more than compensates for the CE damage, at the cost of a small chunk of her NP gauge. Only really appropriate if she gets NP gain support from Tamamo or Nero Bride, however.

Shiki's skill leveling is simple. Her expertise is handling AoE Instant Death to clear mobs and gaining NP. Maxing Mystic Eyes of Death Perception first is a must to make her more consistent.

Her second skill, Unyou, on its own is a good attack buff for 3 turns, but it's worth remembering that Shiki's base attack is not stellar and she relies heavily on this as well as her passive "Connection to the Root" to bring her attack up. Between this skill and Yin-Yang, it will prove a lot more crucial to her role in most general circumstances and should be maxed second.

Yin-Yang is a huge heal at max level on a low cooldown. This coupled with her high health pool make her quite durable for a Servant without dodge / invulnerability. It is a skill worth maxing, although it is best used if she has NP level 2 or higher to avoid wasting her NP bar.